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Author Topic: Powering the Weber MTR and small QRP radios via USB.  (Read 1525 times)

gil

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Powering the Weber MTR and small QRP radios via USB.
« on: June 10, 2015, 12:33:14 AM »
Hello,

I know, you'll say USB is 5V and radios mostly use 12V... Well, yes... But there is such a think as a USB DC 5V to 12V DC-DC Boost Converter! Check Ebay, they go for less than $5. What's the catch? The output is only 400 to 500 mA. The MTR for instance draws about 550mA on transmit, and that is just about over the limit for these voltage boosters. However, we are talking dits and dahs here, so not a 100% duty cycle. Some models have an adjustable output, so at 9V you could draw just about 550mA, but the MTR would draw less at that power level (2.5W), half of the draw at 5W, so presumably less than 300mA. If you fry one, oh well, you bought five anyway ;)

This allows you to use a computer to power your radio! If the USB port can output 2A that is... But there are a flurry of USB batteries available used to charge phones and other USB devices. I am thinking of the Goal Zero Venture 30 for instance, which is a 7800mAh battery pack. I can recharge it with my Nomad 7 solar panel. A car USB charger would do well too. It's just another gadget, yes, but could be very useful when you lack a 12V power source. Many small rigs with a power output of up to 3W would probably work, like a Rock-Mite.

For the adventurous, here is a design with more power, 800mA: http://www.hobby-hour.com/electronics/lm2577-switching-regulator.php

I am not sure they would work mind you, so don't take my word for it. They might be noisy and I don't know what the output looks on a scope. Sure it's supposed to be DC, but how clean is it? Has anyone ever tried one?

I might order two each of a couple designs just to test them...

Gil.
« Last Edit: June 10, 2015, 12:47:44 AM by gil »

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